A control system in a processing facility that processes tangible products (e.g., a manufacturing plant or refinery) includes at least one process controller which integrates (interfaces) with a wide variety of different controller controllable (CC) devices from a plurality of different third-party vendors that can be configured and controlled by the control system (e.g., input/output (I/O) modules and devices such as industrial drives and programmable electronic relays). Such CC devices connect the process controller to a variety of field devices comprising actuators and sensors in the processing facility. The actuators and sensors are not directly configured in the control system, except in the case of smart field devices.
Communications between the process controller and the CC devices is enabled by device templates which are stored at the process controller. Device templates include device description information (data) about the physical and logical blocks that make up the CC device used for the integration of the device with the process controller. Device templates also include other device description information about parameters of the CC device, the device's communication protocol, data format (e.g., serial data or parallel form), status and alarms.
Conventional device templates are pre-built (stored) in the engineering repository of the process controller so that the device description information in the device template is static (fixed) as process controller firmware. The device templates are generally specific (per) device and hence cannot be used for other devices even if they are of same type of device and used for same purpose. Device templates can also be created for a particular type/category of devices, such as for industrial drives. Device templates for an industrial drive can be used to integrate industrial drives into the process control system, but cannot be used for other CC devices such as programmable electronic relays.
The following are likely problems with a conventional plant integration scheme using known static device templates:
1. It is not practical to create static device templates for every CC device that may be used by the customer in the processing facility. In some cases a CC device may be introduced after the release of the process control system. In such a case the new CC device cannot be integrated without releasing a new version of the control system (with a firmware update).
2. Static device templates can only be used to integrate specific device types and cannot be extended to integrate other device types. Static device templates have following characteristics:
I. Addition of a new CC device requires a new development effort. Development work is required to support configuration, control and monitor of the new CC device.
II. Static device templates cannot be guaranteed to work after a firmware upgrade of a CC device as it may have become inconsistent with the new revision of device firmware. This limitation can force the customer to use a specific device firmware version; and this may not be practical if there are any critical patches in the newer revision of the firmware.
III. There is generally no way for the user to add any additional parameter(s) from a given CC device other than what is already available in the static device template. Parameters available from a given CC device depend on the type and make (manufacturer) of a particular device. For example, consider an industrial drive where the device template includes parameters for controlling the speed and customer's application and the customer would like to add additional parameters to also control the torque and position of the industrial drive. This can only be done by modifying the device template which requires a development effort and another release of the device template product.
IV. A failed CC device cannot be replaced with a new version of the same device as it cannot be guaranteed to work because the device template is dependent on the firmware associated with the device. New firmware for a CC device may not support the feature and data format used in the control system so that the device template cannot be guaranteed to work.
3. Static device templates based on standard device profiles do not allow use of the extended capability(ies) of the CC device. Device templates based on standard profiles provide an interface that contain features common to devices of the same category and do not expose extended capabilities of the device to enable their use. Static device templates do allow CC devices of a similar category to be integrated into the control system, but do not allow extended capability(ies) of the device to be used beyond the standard set of capabilities defined in the static device template. Using this least common denominator approach can dumb down an otherwise intelligent CC device in the control system.
4. The vendor supplied device description file (e.g., electronic data sheet (EDS) file) for common industrial protocol (CIP) or device description (DD) file for Foundation Fieldbus (FF) of the CC device may not have sufficient details to generate a device template; and in some cases such details may not even be available. For example, the CIP standard proposes use of the EDS file associated with the device to define its capabilities. This file is created by the device vendor and contains information about device identification including configuration parameters and connection details.